This was part of a promotional campaign related to the release of Call of Duty: Modern Warfare 3.

According to the press release:

Basketball superstars Kevin Garnett and Russell Westbrook attend the first-ever Call of Duty XP at the Stages in Playa Vista, Calif. Garnett and Westbrook each led a team military servicemen and Call of Duty XP attendees in the ultimate Pros vs. GI Joes Call of Duty Grudge Match.